The use of endoscopic instruments and the adaption of video camera technology to endoscopic imaging has proven to be quite advantageous in a wide variety of surgical procedures and general diagnostic applications. Typically, an endoscopic instrument includes an elongated probe for use in penetrating and viewing remote and otherwise inaccessible body regions. Various endoscopic devices and surgical techniques have enabled the simplification of many surgical operations, and examples of commonly used endoscopic instruments include the laparascope, cystoscope, arthroscope, bronchoscope, and the colonoscope, whose names are obviously indicative of their functions and anatomical areas of use.
Conventional video endoscopic systems include an endoscope, an optical adapter and a video camera head. Before each use, the endoscopic system must be adequately cleaned and sterilized, such as by soaking or immersion in a sterilizing or disinfecting solution and/or sterilization by use of ethylene oxide gas. Conventional endoscopic devices require the surgeon to view the target area directly through the eyepiece of the endoscope, which typically necessitated the surgeon bending over or otherwise situating himself in awkward positions so as to be able to view through the eyepiece. Video camera technology has been adapted to overcome these kind of inconveniences and a typical assembly for adapting such camera technology to an endoscope includes an ocular assembly for focusing the visual image from the eyepiece for remote viewing, with such assembly including a mechanism for grasping the endoscopic eyepiece and coupling the same to the camera head. The coupling device generally has a fitting at its proximal end which attaches to the video camera or an adapter unit attached to the camera head. The distal end of the coupler comprises the mechanism for grasping the endoscopic eyepiece. Often the adapter unit includes adjustable viewing optics for the video camera to provide for focusing, zoom characteristics and the like.
To provide the adjustable viewing optics required for optimal performance and clarity in these endoscopic arrangements, the moving parts of the focusing optics are most preferrably sealed within a housing which protects the optics themselves from direct contact with the environment and with cleaning solutions and the high pressures often encountered in sterilization techniques. Heretofore, optical devices including the moving parts of focusing optics have been provided with a plurality of O-ring type seals which rotate or slide between various moving parts to provide a leak-tight seal U.S. Pat. No. 4,779,613, which issued to T. Hashiguchi, et al. on Oct. 25, 1988, is an example of an endoscope which incorporates the use of a plurality of O-rings to allegedly provide an air-tight seal of its focusing lens. In particular, Hashiguchi, et al. contemplate the use of O-rings or silicon or epoxy based cement to prevent moisture from entering the optical system. It has been observed, however, that in order to obtain a good seal between adjacent parts utilizing O-ring type seals, a relatively high compression force must be maintained upon such seals.
In structures requiring a leak-tight seal between actual moving parts of an assembly, the required compression forces inherently increase the difficulty with which the pieces are moved relative to one another in use, and tend to break down the integrity of the O-rings in use. Moreover relative movement of the focusing optics is often accomplished by rotation of an adjustment knob which, in turn, moves one or more focusing lens along a focal axis. Consequently, in addition to longitudinal reciprocation, O-rings may also be subjected to relative rotational movement as well. Such constant wear and stress can compromise the integrity of even the most hermetic of seals over time, and may also require intricate and often time consuming maintenance and replacement programs. Any moisture which penetrates past the O-ring or cement seals during use and/or cleaning and sterilization procedures can make its way onto the focusing optics in use in the form of fogging or condensation, thereby interfering with the operator's view through the device.
Another approach to sealing a lens mounting system is set forth in U.S. Pat. No. 4,718,750, which issued to R. Forkey on Jan. 12, 1988. The Forkey lenses mounting system utilizes interacting threaded components to provide for axial adjustment of a lens mounting assembly, particularly depending upon lubrication between the threads to provide a fluid seal. The lubricating material is intended to serve both to lubricate the interacting threads of the rotatable members of the Forkey device and to provide the vapor fluid sealing function between the rotatable threaded members. In this arrangement, an external sleeve is pinned to a lens carrier held within the assembly for rotation relative to the centrally mounted body assembly. A second pin extends through the body assembly and into a helical groove formed in the lens carrier, so that relative rotation between the external sleeve and the body assembly causes the lens carrier to longitudinally reciprocate within the device.
While the Forky disclosure discusses a liquid tight seal against internal/external pressure differences, those pressures, heat and the caustic sterilization fluids generally utilized to clean and sterilize devices such as endoscopes used in surgical procedures, can quickly break down lubricants such as petroleum jelly and grease as contemplated in the Forky reference. Additionally, it is well known that repeated application of water and other fluids to grease and the like tends to break down these substances and could similarly compromise the fluid tight seal created thereby.
The axial adjustment of lens devices as a result of relative rotational movement between adjacent telescoping pieces has been widely used in the camera and lens industry. U.S. Pat. No. 2,818,768 (which issued to M. Updegraff on Jan. 7, 1958) and U.S. Pat. No. 4,030,113 (which issued to C. Obreschkow on Jun. 14, 1977) are examples of various camera and photographic equipment incorporating the use of relatively rotating parts to reciprocate a lens carrier focusing assembly. These structures, however, similarly fail to provide for adequate sealing of the reciprocating lens assembly to ensure a moisture and vapor proof seal for preventing condensation and/or fogging of the lens components in use.
An adjustable ocular mounting arrangement is also shown in U.S. Pat. No. 2,851,924, which issued to G. H. Beusker on Sep. 16, 1958. The Beusker disclosure acknowledges the problem in prior art sealing means which require a sliding seal between moving parts. As disclosed, the Beusker device includes a sleeve within which a plurality of lenses are hermetically sealed, with portions of the sleeve adapted to be longitudinally reciprocated in response to relative rotational movement between an adjusting ring and an ocular casing. In particular, the ocular casing is moved axially by relative rotation between the adjusting sleeve and such casing. The sleeve in which the lenses are secured is sealed within the casing by means of an expandable rubber bellows section. While this arrangement would appear to provide a liquid and air tight adjustable ocular arrangement which obviates a need for a sliding seal arrangement, its substantially closed construction and rubber bellows arrangement does not lend itself to facilitating cleaning procedures or to resisting the caustic cleaning solutions and high pressures and temperatures generally associated with repeated cleaning and sterilization procedures for surgical instruments and the like. Particularly, the rubber bellows would be subject to many of the same breakdown and maintenance problems discussed above with regard to O-ring type seals, and the Beusker device would require substantial disassembly to complete proper cleaning and sterilization procedures between uses.
Consequently, heretofore there has not been available in the industry a relatively simple, reliable, and durable leak-tight sterilizable adjustable optical assembly for use in endoscopic applications and similar optical setups where repeated cleaning and sterilization is necessary between uses, and wherein varying environments of moisture and high pressure are encountered. While various sealing arrangements have been provided in the industry from time to time, many require dynamic sealing arrangements and/or the use of sealing materials which are subject to degradation in relatively hostile environments of use, clean up and sterilization. Assemblies sealed with O-rings also generally require high compressive forces on the moveable seals, imposing deleterious forces on the rings and making adjustment movement more difficult. Additionally, the resulting structure of the adjustable focusing devices available heretofore have often required substantial disassembly for proper cleaning and sterilization between uses, requiring inconvenient and time consuming maintenance and replacement work. These devices have been unable to ensure the avoidance of fogging and/or condensation on the various focusing lens in use on an ongoing basis.